1. Field of the Invention
This invention relates to a display apparatus employing a Liquid crystal panel, and more particularly to a data driving circuit for a liquid crystal panel that drives the liquid crystal panel with a digital image signal.
2. Description of the Prior Art
Recently, in image media, there has been a trend toward the use of digital, as opposed to analog, image signals. Digital image signals San be more easily compressed, providing a high resolution picture to a viewer. As a result, it becomes desirable for liquid crystal displays to be driven by analog as well as digital image signals. According to the driving circuit for the liquid crystal display panel has been configured to be adaptable for driving picture elements(or pixels) in a liquid crystal panel requiring an analog signal. As a result, in the liquid crystal display apparatus, analog-type data driving circuits now coexist with digital-type data driving circuits.
Since each digital-type data driving circuits process pixel data in parallel, they require high capacity of memories and use digital to analog D-A converters having a complex circuit configuration. As shown in FIG. 1, in order to drive data lines DL1 to DL2400, the digital-type data driving circuit 20 includes first latches 22 connected to data buses DB1 to DB3, and second latches 24, and a digital to analog(D-A) converter array 26 cascade-connected to the first latches 22. The first and second latch arrays 22 and 24 include 2400 latches, respectively. Each of the latches has a length of 6 bits to receive 6 bit pixel data.
That is, as shown in FIG. 2, the latches included in the first and second latches 22 and 24 each include six 1-bit latches which each consist of two inverters INV1 and INV2, an MOS transistor MN1 and a capacitor C1. The 2400 latches in the first latch array 22 are sequentially driven in accordance with a logical value of an output signal of a shift register 28 to sample 6 bits of red(R), green(G) or blue(3) color pixel data from the data bus DB. The first latch array 22 temporarily stores R, G and S pixel data for one line, that is, 2400 pixel data. The 2400 latches included in the second latch array 24 respectively receive pixel data from the 2400 latches in the first latch array 22 simultaneously, and transfer the received pixel data to the D-A converter array 26. The D-A converter array 26 converts the 2400 pixel data received from the second Latch array 24 into pixel signals, and applies the converted 2400 pixel signals to the 2400 data lines DL1 to DL 2400 in the liquid crystal panel 10, respectively. To this end, the D-A converter array 26 includes 2400 D-A converters. Each of these 2400 D-A converters receives 6 bit pixel data simultaneously and generates a pixel signal having voltage level that differs in accordance with a logical value of the 6 bit pixel data.
Meanwhile, in liquid crystal display devices, there has been a trend toward integrating the data driving circuit on the liquid crystal panel in order to reduce its bulk size. When integrating the data driving circuit on the liquid crystal panel, the size of liquid crystal panel becomes enlarged memories and complex D-A converters are typically large components. More specifically, since it is difficult to achieve a fine pitch by forming poly-silicon thin film transistors at a low temperature, the data driving circuit occupies an increasing wide area of the liquid crystal panel.
It is an object of the present invention to provide a data driving circuit for a liquid crystal pane having a simplified circuit configuration and being capable of integration on the liquid crystal panel.
In order to attain this and other objects of the invention, a data driving circuit for a liquid crystal panel includes data input lines for inputting video data in serial, a sampling cell array for sampling the video data inputted in serial from the data input lines, a serial digital to analog conversion cell array for converting the video data inputted in serial from each sampling cell in the sampling cell array into analog signals to apply the converted analog signals to each data lines in the liquid crystal panel, and sampling control means for supplying sequence pulses enabled exclusively and sequentially to each sampling cell included in the sampling cell array, thereby allowing the respective sampling cell to sample a predetermined bit number of data sequentially.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of example only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.